There is a need in the end point detection art for devices and methods that allow for the rapid, accurate determination of analyte (e.g., glucose, triglyceride, cholesterol, etc.) concentration in very small sample volumes of biological fluid. The need for a device using small sample volumes is particularly relevant to the detection of blood glucose because of the difficulty and inconvenience of obtaining blood samples from subjects.
Currently available such devices include ACCUCHEK EASY TEST STRIPS.TM. and ACCUTREND.RTM. (Boehringer Mannheim Corp.). Those devices are multilayer reagent systems characterized by the absence of a buffering agent in the separation or filtration layer.
Buffer is commonly added to the composition present in a detection layer for the purpose of controlling the pH of the reagent composition present in said layer. The use of buffers for this purpose is described, for example, in U.S. Pat. No. 5,116,763.
The present invention provides a detection device having a HEPES-impregnated separation matrix, which HEPES serves to reduce the time needed for analyte detection. Unexpectedly, HEPES speeds up the end point determination in the detection layer. Other buffers do not demonstrate the same benefit.